Oilfield fluids (e.g., oil, gas, and water) are complex mixtures of aliphatic hydrocarbons, aromatics, hetero-atomic molecules, anionic and cationic salts, acids, sands, silts, clays and a vast array of other components. The nature of these fluids combined with the severe conditions of heat, pressure, and turbulence to which they are often subjected during retrieval, are contributory factors to paraffin deposition (including the precipitation of wax crystals), emulsification (both water-in-oil and oil-in-water), gas hydrate formation, corrosion and asphaltene precipitation in oil and/or gas production wells and surface equipment. This, in turn, decreases permeability of the subterranean formation, reduces well productivity and shortens the lifetime of production equipment. In order to rid such unwanted deposits and precipitates from wells and equipment, it is necessary to stop the production which is both time-consuming and costly
For instance, paraffin hydrocarbon waxes which tend to precipitate and crystallize at low temperatures, cause oil to lose its fluidity. Over a range of temperatures, these paraffin wax crystals continue to aggregate and may even solidify the oil. This creates difficulties in transporting the petroleum fuel or crude oil through flow lines, valves, and pumps. Paraffin wax crystals are particularly problematic at lower temperatures and in colder climates where, as the temperature drops and approaches the crude oil's pour point, the transportation of crude oil becomes more difficult. Once out of solution, paraffin wax crystals often plug flow lines, production tubing, flow lines, screens and filters.
Various well treatment agents are often used in production wells to prevent the deleterious effects caused by such formations and precipitates. For instance, pour point depressants and wax crystal modifiers have been used to change the nature of wax crystals that precipitate from the petroleum fuel or crude oil, thereby reducing the tendency of wax crystals to set into a gel.
It is essential that such well treatment agents be placed into contact with the oilfield fluids contained in the formation before such fluids enter the wellbore where deleterious effects are commonly encountered. Several methods are known in the art for introducing such well treatment agents into production wells. A principal disadvantage of such prior art methods is the difficulty in releasing the well treatment agent into the well over a sustained period of time. As a result, treatments must repeatedly be undertaken to ensure that the requisite level of well treatment agent is continuously present in the well. Such treatments result in lost production revenue due to down time.
Treatment methods are therefore sought for introducing well treatment agents into oil and/or gas wells wherein the well treatment agent may be released over a sustained period of time. It is desired that such methods not require continuous attention of operators over prolonged periods.